Removed
Even though it was quite advantageous to be able to cultivate while finishing an annoying task, not everything was great.
In the end, cultivating with the mana that was led through the black flame thread caused his progress in removing the mass of ocean materials to slow down tremendously. He had to split between keeping an eye on the black flame thread and the fact that he had to annex the neutral mana.
Furthermore, it was important to not let the black flame thread touch the mana vein. Even the slightest contact could damage it, or worse, the black flame thread could get out of control because of the mana that would surge into it.
As such, everything took much longer than Jason could hope for. Even his previous estimate of taking only two days, at most, was not even close to the time he had truly required.